docs: def _get_top_of_rupture_depth_term(self, C, imt, rup):
          """
          Compute and return top of rupture depth term. See paragraph
          'Depth-to-Top of Rupture Model', page 1042.
          """
          if rup.ztor >= 20.0:
              return C['a15']
          else:
              return C['a15'] * rup.ztor / 20.0